Fire resistance with CLT is not provided by chemicals. When it burns, the wood chars on the outside which then insulates the rest of the wood. So, it takes quit

Fire resistance with CLT is not provided by chemicals. When it burns, the wood chars on the outside which then insulates the rest of the wood. So, it takes quite some time for this to escalate to the point where the structural integrity is compromised. And it takes quite a bit of heat to keep it burning to begin with. Basically, eventually it would fail if you don't extinguish the fire. But this takes quite some time. CLT is basically rated for how long that takes. As for toxicity, CLT is basically laminated wood with modest amounts of glue (compared to other laminated woods that people use in their homes without much issues). Mostly the glue stays on the inside where the layers are. And of course the glues used have all sorts of desirable properties with respect to not being toxic, bad for the environment, etc.